RSM741 - 메탄 센서
RSM741 for detection of Methane gas (CH4)

1. Features

    High sensitivity to Methane gases
    Low power consumption
      Approx. 300mW @ 5.0V supply
    Small size
    Metal can type package - TO-5
    Uses simple electrical circuit

2. Applications

    Portable gas detectors
    IoT devices
    Ventilation control
    Gas alarm device

3. Package image

Figure 1. Sensor package (TO-5)

4. Description

The RSM741 is a metal oxide semiconductor type sensor in which a sensor layer and a heater layer are formed on an alumina substrate. It can detect the methane (CH4) gas In the sensor, the sensing materials are placed on the alumina substrate , and the resistance of the sensing material is varied according to the concentration of the methane (CH4) gas The RSM741 is fabricated on the TO-5 package with several holes. It can reduce the influence of interference gases as well as protect from humidity or dust.
Typical application circuit
The sensor requires voltage input: Heater voltage (+5V). The heater voltage (H+, H-) is applied to the integrated heater in order to maintain the sensing element at a specific temperature which is optimal for sensing.
Also, input voltage (+5V) is applied to allow measurement of of voltage across a load resistor (RL) which is connected in series with the sensor. The value of the load resistor (RL) should be chosen to optimize the alarm threshold value, keeping power consumption of the semiconductor below a limit of 30mW. Power consumption will be highest when the value of Rs is equal to RL on exposure to gas.
Figure 2. Basic measurement circuit

5. Pin configuration and connections

The pin configuration of RSM711 gas sensor is as follows.
Pin No.
Ground (G)
Heater (H-)
Ground (G)
Sensing electrode (S-)
Output (O)
Sensing electrode (S+)
Power supply (P)
Heater (H+)
Figure 3. RSM741 Pin connections

6. Specifications

Model name
Sensing principle
MOS type
Standard package
Target gases
Methane (CH4)
Typical detection range
500~10,000 ppm
Heater voltage (VH)
5.0 Vdc
Heater resistance (RH)
Approx. 59 ohm at RT
Heater current (IH)
56 +/- 5 mA
Heater power consumption (PH)
280 +/- 25 mW (typical)
Sensor resistance (RS)
0.5~5.0 M-ohm in Air
(Change ratio of RS)
(Rs/Rs-air @CH4 1,000 ppm)
Standard test conditions
Normal air at 25+/-2 C
40+/-5 %RH
Conditioning period
before test
3-days or longer

7. Sensitivity Characteristics

The figure below represents typical sensitivity characteristics, all data having been gathered at standard test conditions.
Figure 4. Sensitivity Charecteristics
Rs = Sensor resistance in displayed gases at various concentrations Ro = Sensor resistance in 5000ppm of methane (CH4)

8. Application guidance

Heater voltage is applied to the heater to maintain a specific temperature at which the sensing material is optimized for detection. DC voltage is required for the circuit.
Since the output of the sensor is a resistance, a conventional measurement part should have a current source in parallel with the output of the sensor to convert the resistance to voltage.
The change of the sensor resistance (RS) is obtained as the change of the output voltage across a load resistor (RL) which is connected in series with the sensor.

9. Outline dimensions

Figure 5. Structure and dimensions
RSM741_Application report rev.0.1.pdf
Last modified 6mo ago